材料期刊网

在不同磁感应强度下对固态Al2O3增强7055铝基复合材料进行了脉冲磁场处理.经脉冲磁场处理后,铝基复合材料的位错密度随磁感应强度的增加呈上升趋势,分析原因在于位错应变能增加和位错钉扎中心自由基对状态的改变.随着磁感应强度的提高,晶内析出相的取向性减小,数量和尺寸增加;晶界析出相由连续状态转变为断开状态,析出相数量减少、尺寸增大,并出现了明显的无沉淀析出带.这些现象主要源于磁场作用增强了晶体内部溶质原子和空位的扩散;畸变能增加、内应力的释放为析出相析出、长大提供了驱动力.力学性能随磁感应强度的增加,呈现出先升高、后降低的趋势.在B=3 T时,抗拉强度、延伸率和显微硬度达到了548.04MPa、17.235％和1224MPa,较处理前试样分别提高了10.3％、16.2％和20.7％.力学性能的改善主要源于位错密度增加造成的位错强化和第二相强化.

Al2O3 reinforced 7055 aluminum matrix composite was subjected to a pulsed magnetic field treatment with different induced intensities (B).Results show that the dislocation density in the composites increases when the B rises from 0,1,3 to 5 T due to the enhancement of strain energy of dislocation and the transition from S to T for the radicals between the dislocation and pinning center.Meanwhile,the orientation tendency of intragranular precipitates is lowered,together with the increase of amount and size.For the precipitates at grain boundary,the morphology has transformed from continuous to disconnected states.The precipitation amount decreases while the size increases.It is highlighted that the precipitation free zone can be found because the magnetic field accelerates the diffusion of solute atoms and vacancies.The increased distortion energy and internal stress facilitate the precipitating and growing process.The mechanical properties rise firstly and then decline.When B equals to 3 T,the tensile strength,elongation and micro hardness reach to 548.04 MPa,17.235％ and 1224 MPa,which are increased by 10.3％,16.2％ and 20.7％,respectively,compared to the initial sample without any magnetic field treatment.The strengthening mechanisms are attributed to the dislocation strengthening and second phase strengthening.